Technologies for calibrating a projection unit which projects multiple light rays are known (refer to, for example, Patent Documents 1 through 3).
However, the technologies disclosed in Patent Documents 1 through 3 do not provide a calibration method for calibrating such a projection unit that includes an optical system which is different from a pinhole optical system that emits multiple light rays from a single specific point (hereinafter, also referred to as “non-pinhole optical system”).